[bshipp]

Extra effort from the engines? That sounds a little silly, like they just need to be motivated to work a little harder. Take-off power is take-off power.

Reduced air density just means the engines don't produce as much power and the wings don't generate as much lift; a double-whammy of lower available engine thrust and greater speed required for the same takeoff roll.

[DuskStar]

> Take-off power is take-off power.

I don't think it is anymore - not with noise abatement rules. You can take off in X meters with 100% throttle, or 2X with 80% - but the runway is 4X meters, so you takeoff with reduced throttle to make things quieter for the neighbors.

[chopin]

I don't know whether there are really regulations for that but as a pilot (which I am not) I would not want this as this would lower the decision velocity (I think it's v2) after which the start can't be aborted.